Blower



Aug. 29, 1 944.

M. RENDELSTEIN BLOWER Filed Oct. 25, 1959 Patented Aug. 29, 1944 BLOWER Max Rendelstein, Brussels, Belgium; vested in the Alien Property Custodian Application October 25, 1939, Serial No. 301,295 In Belgium October 24, 1938 1 Claim.

This invention relates to means for increasing the effective output of the propellers, of aeromotors and of similar rotating devices. It is known that the effective output of such devices is based on the resistance offered by the fluid in which the device under consideration functions. Starting from-the ascertainment of the fact that the effective output can be increased with the density of the medium, the process according to the invention consists essentially in producing alternate compression and relaxation or expansion of the fluid on all sides of the device, as the device rotates.

'jIn the following description, for simplicitys sake, one will suppose that the invention concerns a bladed screw or propeller revolving in the air, but the invention is applicable to any rotative devic revolving in any fluid medium whatever.

, The process according to the invention will be described with reference to the annexed drawing which represents some devices, given as nonlimitative examples, for the realization of the process. On the drawing,

Fig. 1 shows a vertical section of a device constructed in accordance with the invention, and I Fig. 2 shows it in vertical section taken along the lin 22 of Fig. 1.

Fig. 3 shows schematically another form of embodiment of the device,

Fig.4; shows a front view of a perforated disc which forms part of the device shown in Figure 3. shows the invention .applied to an aeroplan'e.'

According to Figs. 1 and 2, a bladed screw or propeller 4 is keyed on the shaft 5 which is operated by means of the pulley 6 and the belt I. A cellular wheel Ill is provided on either side of the propeller, consisting of a rim I and of the radial" partitions 2 which start at the hub 3 and divide the wheel in compartments 9. The cellular wheels are fixed on a base 8 and their hubs act as bearings for the shaft 5. The propeller 4 owing to its revolutions produces a current of air in the direction of the arrow P. Owing to the presence of the cellular wheels on either side of the propeller 4, the flow of this current of air is modified in density at very frequent intervals as the propeller rotates because the'air has a tendency to be compressed while confined in the cells 9. e As the relatively dense or compressed bodies of .air leave the cells, pulsations which are short-lived, follow one another continually, the result being an increase of the effective output of th propeller, because of the expanding effect of the said bodies of air. as they escape from the cells 9.

' The widthof .thepropeller blades, or the depth of the cells is advantageously regulated, and for this purpose each cellular wheel can, for instance, be made of two similar parts which telescope one in the other .ina radial direction, which allows the optimum depth. of the cells to be determined in each case.

A further embodiment ,of the invention is schematically shown in Fig. 3. A ventilator ll exhausts the air of chamber l3 by means. of a conduit I5 in thedirection of the arrow R, and delivers it, always in the direction of the arrow R, through the conduit l6 into the chamber l4. Before the open terminal face of each of the chambers l3 and I4 is a pair of stationary cellular wheels I0, fixed on a base 8 and in which rupted which gives rise to .a rapid succession of compressions and expansions in the current of air. The device represented may serve, for instance, as a compressor, or as a blower, and allows notably large masses of air to be delivered with a reduced consumption of power.

The propellers, aeromotors, etc., actually known derive their efficiency from the resistance which an air mass opposes to its being itself set in motion. The effective output is determined by the quantity of air whichcomes in direct contact with the surface which sets this air in motion, and by the speed '11 which the surface in motion imparts to it. If F is the surface of th blades which set. the air in motion, one has W=k. p. F11

where W designates the power which must act on a volume of air F11 in the time unit, to impart to it the speed 'U. As the total surface of the blades of a propeller is smaller than the surface of the circle described by the blades, the power of traction, for instance in the traction propellers, necessarily remains smaller than the power required to communicate the speed '0 to the air mass crossing the whole of the circular surface.

It is only the mass of air in direct contact with the surfac ofthe blades which produces an effect. According to the invention, successive compressions and expansions are produced in the generated air current which transmit themselves in opposite directions starting from the point at which they are produced, with the speed of sound. In the application of the invention to aeromotors, the rate of revolution of the wheel of the aeromotor must be brought up to an appropriate speed by employment of sufficient power. driven by a motor, the traction power is equal to the power required to impart the speed 17 to an air mass 2, say, 330 F. The air resistance being, in this latter case, designated by W2, one has The efficiency of the process according to the invention is based on the following considerations: Supposing, in a long tube of section F, a mobile surface occupying exactly the section of the tube, it is evident that when the surface displaces itself, and a corresponding body of air in the tube, the air cannot escape laterally. When the surface displaces itself at th speed 11, the layers of air which are at a distance from the surface must progressively follow the same movement as it. A certain time is required t for a layer of air separated from the surface F by the distance Z to take this motion. During this time, however, the surfac F has described a path t.v, and consequently compressed a volume of air LP to the volume (1-tv) F. During this time, at the back of the surf-ace in motion, an expansion or relaxation of air is produced, the volume of air 1.F having expanded to the volume (1+tv) F. The speed with which the surface movement imparts itself to themost distant air layers is equal to the speed of sound, and the resistance which the surface meets with is equal to the normal atmospheric pressure. If at a pressure of about Wz='70.F.v kg. If the mobile surface stops, compression of the furthest removed air layers, situated on either side of the surface, terminates progressively, and the air resumes its normal density, and their movement transmits itself to air layers which are further away.

Supposing a tube having a length L and calculating the speed of sound as 330 m./sec., the above resistance will only exist during the time taking into account the duration of the propagation before and behind the surface F.) from the start of the movement. If, after this period of time, the surface continues to displace itself whereas the air coming out of the tube can escape in all directions, the changes in density diminish toward zero. As a matter of fact, the compression and the expansion described which propagate themselves with the speed of sound, only take place within the tube. Variations of density which propagate themselves, can also produce themselves in the open air, if the weak duration of the movement is comparable to that of the sound oscillations. If the length L of the tube is so small that the time L am is near to the duration of an oscillation 01 a In the case of a traction propeller,

sound emitter, the compressions and expansions caused in the tube by the movement of the mobile surface during the time t will still propagate themselves, at the speed of sound, in the open air after having left the tube, whereas the air in the tube returns to a state of rest, when after a time the movement of the mobile surface has ceased. The resistance met by the mobile surface during the time t is again equal to W2=70.F.v kg.

The speed of the revolutions of the propeller 4 or of the disc H is predetermined in such a manner that the duration of the pulsations caused by these devices will be as nearly as possible the same as the duration of the sound oscillations. It is sufficient if a rate of 2 /2000 sec., exists which can be obtained by the peripheral speed of the revolution of the propeller 4 or of the discs ll near to the speed of sound.

' However, for reasons of practical realization, one may choose U=Ic.330, with k 1, U being the effective peripheric speed.

The following relations:

W2 70-FJ) allow one to predetermine, in each case considered, the power, and the effective output, as well as the dimensions of the propeller or of the disc, the number of blades, the width and the pitch of the blades, the number of cells, etc.

The number of blades of the propeller 4 depends on the number of cells 9. The revolution speed being suitably determined, the blades produce on one face, an air rarefaction, and on the other face, an air compression, like the mobile surface in the example described hereinabove.

If the number of revolutions of the propeller,

" the width of the blades, and the number of cells 9 present a relation such that between the obturation of a cell by a blade and the reopening of the cell, the compression or the air expanded in the cell has not had time to transmit itself to the exterior of the cell, that is to say, to come out of the cell, the effect is then identical with that of the example of the tube above given.

The device according to the invention is applicable to propellers in general, especially to aeroplane propellers, to aeromotors, to the wheels of static parachutes, etc.

Fig. 5 shows schematically an application of the invention to an aeroplane wherein lifting surfaces are replaced by propellers according to Fig. 1. It will be understood that one or more such similar propellers can be utilised as driving propellers for aeroplanes.

Having now fully described my said invention, what I claim and desire to secure by Letters Patent, is:

A blower or the like comprising a first air chamber, a first circular air compressing member positioned across a conforming air intake opening formed in a side of said first air chamber, a ventilator at the opposite end of said first chamber, said ventilator having a substantially axial intake conduit leading from said first chamber and an eccentric discharge conduit, a second air chamber at the opposite side of said ventilator .39?) $8411 first air chamber and with which said discharge conduit is connected, a second circular air compressing member positioned across a conforming air outlet opening formed in the outer side of said second air chamber, each of said air compressing members consisting of a pair of substantially similar slightly axially spaced elements each consisting of a circular rim having uniformly circumferentially spaced radial spokes which have relatively great width in the axial direction and a hub in which the radially inward ends of the spokes terminate, the spaces between adjacent spokes and the rim defining segmental air confining pockets, and a rotary disc substantially occupying the space between the said elements and coaxial therewith, said disc being formed with uniformly circumferentially spaced segmental openings defining imperforate segmental shutters therebetween, the segmental openings being slightly narrower than and the segmental shutters being slightly wider than the segmental spaces 

